/*清除默认样式*/
body, ul, li, p{
    margin:0;
    padding: 0;
}
html{
    background-color:#f4f5f5;
}
a{
    text-decoration: none;
    color:#333;
}
ul {
    list-style: none;
}
button{
    outline: none;
    transition: background-color .3s,color .3s;
    cursor: pointer;
}
